Master clock



Dec. 8, 1953 R. B. JOHNSON EIAL 2,661,590

MASTER CLOCK Filed Jan. 7, 1948 ,Sheets-Sheet 1 INVENTORS REYNOLD B.OHNSON EDWARD F.GEIGER R. B. JOHNSON ETAL 2,661,590

MASTER CLOCK 4 Sheets-Sheet 2 JOHNSON R m m4. m NW A Y ED i m 21 Nm mv E8 mm & N 3 E ON om E lJllfil N H a p K, S w. 3. {w (A. E h x T8? 8w 3 2L Q2 h Nu .K 8N No E E S. T@ MW 5 o: 3N ON E u o h 3. u Q w ,MWH. nwn wwwmmww MHHH M lllll i a s s. m X:

Dec. 8, 1953 Filed Jan. 7, 194s AGE N'T Dec. 8, 1953 R. B. JOHNSON ETAL2,661,590

MASTER CLOCK Filed Jan. 7, 1948 4 Sheets-Sheet 3 IN [[LllllllllllIlllllllllflk INVENTORS REYNQLD B. JOHNSON EDWARD FZGEIGER D60. 8. 1953R. B. JOHNSON EIAL 7 2,661,590

MASTER CLOCK Filed Jan. 7, 1948 4 Sheets-Sheet 4 INVENTORS REYNOLD B.JOHNSON EDWARD F. G'EIGER 36%8 4 AG-ENT Patented Dec. 8, 1953 MASTERCLOCK Reynold B. J johnson and Edward F! Geiger;,Bing-. hamtcn, N. Y'.,assignors to International Busi ness- Machines Gorporatiom New York, N.Y., a.

corporation of, New York Application January 7, 1948,, SerialNo. 990

4 Claims.

1 The present invention relates to clock systems in general and inparticular to improvements. in

commonlyused cally synchronized withv the master clock at regularintervals of time.

Specifically, the invention relates to a. masterclock which operates. tosend electrical impulses at: regular intervals. of time to. all of theSecond;- ary" clocks. associated therewith in the system and each.secondary clock is: advanced a predetermined amount upon receiving eachimpulse. In addition to this, the. master clock during; certainpredetermined intervals of time automatically-- regulates,v and effects.synchronization with the master clock of any of thesecondary clockswhich may be fast: or slow. An example of a master clock. and anexplanation of how such. a clock functions in a clock system, are. fullydisclosed in the U.. 8.. patent to Larrabee, NO... 1,878,931, datedSeptember 20,. 1932.

Herctoiore, master clocks of the type briefly outlinedabove have beendriven eitherby a synchronous electric motor operated by current flowfrom the commercial light and power line. or they received their powerfrom, a spring-wound motor. Additionally, it, has been proposed: thatwhere the master clock is normally driven by a syn.- chronous electricmotor operated from the power line that a standby or auxiliary motor bepro.- vided to operate and drive the time indicating element at thecorrect time rate in case the synchronous: motor fails to operateefie.ctively., An example of this latter type of master; clock; is shownin the U. S. patent to; East No. 2,424,119, datedv July 15, 1947.

v The present invention is designed as. an. improvement over the masterclocks. shown and de: scribed in the above mentioned patentsand, to.-ward this end, it is amongthe principal objects oi the invention toprovide a. master clock, usable in systems of the type outlined above,and having associated therewith a moving element which is continuouslydriven from a spring-wound motor and another moving element which movesin synchronism with. a source of current supply, which may be the usual.(SO-cycle current flow derived from a commercial light and power line,together with automatic means for regulating the rate of rotation of thecontinuously moving element to coincide with the. rate of rotation oithe: synchronously moving element to the end that, the rate of rotationof both of these elements shal be made the. same. It is thusv obviousthat. in case of a power line failure which brings the synchronouslymoving element to rest, the conv tinuQusly' rota-ting element will;continue to move. at the same rate: as the sy hronous y m in lement,thereby bridging over the hiatusduring; which; there is no currentsupply.

A further andrelated object of the invention is to, provide: regulatingmechanism for performms the in otionsbriefly outlined above which, willremain effect. only during such time as both the: continuously movingspring driven; ele: ment and the synchronously driven element arebothinv operation and which will become auto-. mati allv inoper e e' e hthe yn:- chronously driven element comes to rest, It 011. lows,therefore, that at the precise instant oi a poweriailure the regulatingmechanism will have brought the. continuous rota e n int exactsynchronismvvith, the synchronously driven element; so, that the formerwill tide the master clock; over; so tospeak, until such time as poweris. resumed-i and that if, the hiatus exists over a comparatively longperiod, of time so.- that. a dis: crepancybetween the rate of rotationof the continuously driven element and of the synchronously drivenelement exists when power is resumed suitable. correction will beinstantly and automatically made when such power resumption occurs.

The,- mechanical details and the features, of construction which arenecessary to provide an operative: structure capable of functioning inkeeping, with the above mentioned objects, are such that in the eventthe spring driven element becomes; stalled for any reason whatsoever,the regulating means will attempt to bring the stalled element intosynchronism with the. synchronously driven element, Since. the springdriven element is stalled and cannot be brought. into such. synchironism as. long as. it is stalled, the regulating means. will move.to. the limit of its position for a fast. setting of the spring drivenelement. The present. construction is so designed that in such an eventwhen an operator again restores or sets the spr n driven; l ment in o.mo ion th re ulating means will immediately become efifective to synchrnize the. two m vin elements without turther. attention onv the part ofthe operator,

It has been the practice, heretofore, to equip master clocks withcertain contacts, that, cooperate with the clock movements to sendimpulses of el ctric current t the secondary c ck a r ular periods. oftime for the purpose of driving the secondary clocks. and also to equipthe master cloc s withaddit onal cont ct or sending rapid. impulses(it-current during the synchronization period to any or the secondaryclocks which may happen to be slow at the commencement of thesynchronization period. An example of a complete master and secondaryclock system may be had by reference to the U. S. patent to Bryce, No.1,687,491, dated October 16, 1928, for a Synchronizing Clock.Additionally, other contacts are sometimes employed in connection withthe master clocks for operating program devices or other auxiliaryequipment from the master clocks. Such contacts have usually been camoperated from the gearing of the clock train of the master clock and therapid impulse contacts have usually been operated from the verge orescapement mechanism of the master clock, all of the contacts incombination placing a relatively heavy drain or torque upon the vergeshaft or other clock escapement mechanism. In accordance with thepresent invention, it is an object thereof to alleviate this relativelyheavy drain on the clock system by removing the rapid impulse contactsfrom any association whatsoever with the spring driven clock mechanismand transferring the same to the driven mechanism associated with thesynchronously driven element. Such a transfer presents no obstacle tothe proper operation of the secondary clocks associated with the masterclock inasmuch as when the current supply is unavailable for driving thesynchronous motor, it is also unavailable for sending rapid impulses tothe secondary clocks and, in any event, during current interruption, thesecondary clocks must await their correcting impulses until such time ascurrent is available for the rapid impulse contacts.

The provision of a master clock possessing the novel features brieflyoutlined above being the principal object of the invention, otherobjects of the invention will be pointed out in the followingdescription and claims and illustrated in the accompanying drawings,which disclose, by way of example, the principle of the invention andthe best mode, which has been contemplated, of applying that principle.

In the drawings:

Fig. 1 is a front elevational view of a master clock constructed inaccordance with the principles of the present invention.

, Fig. 2 is a top plan view of the clock shown in Fig. 1.

Fig. 3 is a sectional view taken substantially along the line 3-3 ofFig. 2 in the direction indicated by the arrows.

Fig. 4 is a sectional view taken substantially along the line t-4 ofFig. 2 in the direction indicated by the arrows.

Fig. 5 is a fragmentary rear view of the structure shown in Figs. 1 and2.

Fig. 6 is a fragmentary exploded view showing a portion of the clockmechanism including a dififerential gear assembly and a regulator armemployed in connection with the present invention.

Fig. 7 is an electrical circuit diagram for the master clock.

In all of the above described views like characters of reference areemployed to designate like parts throughout.

Referring now to the drawings in detail, the master clock involves inits general organization a rear or main supporting plate or casting Infrom which all of the various stationary and moving parts of the clockstructure are supported. This casting H] is of irregular configurationand includes a substantially flat sheet-like forward section I2 and arearwardly offset section I4, the

latter being formed with rearwardly extending tapped and threadedattachment lugs l6 by means of which the casting I!) may be secured to asupporting surface or the like, not shown. A more or less conventionalspring wound clock escapement mechanism is designated in its entirety asan assembly at I8 and includes a front support plate 20 and a rearsupport plate 22, the two plates being held in fixed spaced relationshipby the usual pillars 24. The clock mechanism l8 comprises a timeindicating train which consists of a driven shaft 26 supported forrotation between the two plates 20 and 22. As will be explainedhereinafter, the driven shaft 26 is adapted to be rotated by the clockescapement mechanism once every minute and, as a consequence, this shaftconstitutes the second hand shaft of the clock mechanism l8. Toward thisend, it has mounted thereon, outside of the front plate 20, a secondhand 28 which registers with a seconds indicating dial face 30associated with an integral dial assembly plate 32. The dial assemblyplate 32 also has associated therewith a minutes indicating dial face34, the assembly 32 being of ring-like design and being secured to thefront plate 20 forwardly thereof by means of pillars 3B. The gear trainfor the clock mechanism l8 comprises a large first gear 38 which isloosely mounted on a power shaft 40 and which is attached adjacent itsperipheral regions to the outer end of a coiled spring 39 disposedwithin a winding drum 4|. The other or inner end of the coiled spring 39is suitably secured to the power shaft 40 and the latter shaft isadapted to be periodically indexed or rotated throughout a smallincrement of motion to apply a tension to the coiled spring 39 and thusbias the first gear 38 for proper operation of the gear train of thespring wound clock mechanism. The first gear 38 meshes with a smallsecond gear 42 mounted on a shaft 44 rotatably journaled between thefront and rear plates 20, 22. The shaft 44 is adapted to be rotatedunder the influence of the coiled spring 39 and also under the controlof an escapement mechanism, subsequently to be described, once everyhour and, as a consequence, this shaft constitutes the minute shaft ofthe clock mechanism IB. Toward this end, it has mounted on one endthereof forwardly of the plate 20 a minute hand 46 which cooperates withthe minutes indicating dial face 34. The minute hand 66 forms oneelement of a cam assembly including earns 48 and 50 associated with asynchronizing contact group designated in its entirety at 52, the natureand function of which will be made clear subsequently. The cam assemblyis loosely disposed on the forward end of the minutes shaft 29 and isadapted to be frictionally driven from the latter shaft by means of athree-armed spring element 54 suitably secured to the shaft and the armsof which bear against the inner surface of the assembly.

A large third gear 56 is mounted on the minute hand shaft 44 and mesheswith a small fourth gear 58 mounted on a shaft 60 journaled in the frontand rear plates 20, 22. The shaft 60, as will appear presently, isadapted to be rotated once every seven and one-half minutes or to makeeight revolutions per hour. To control such movement of the shaft 60,this shaft carries a large gear 62 which meshes with a small ear 64mounted on the minute hand shaft 44 and this latter shaft 44 carries alarge gear 66 which meshes with a small gear 68 mounted on theescapement wheel shaft 10 of the clock mechanism. I18; The shaft. I isrotatably "journaled between. the front andrear plates 20',v 2'2 andcarries. an escapement; wheel I25 which co.- operates with the palletsurfaces on the. usual verge element: M mounted on the: verge. shaft?and associated with the escapement assembly; This latter assemblyincludes a conventional fork member 'I Gi mounted on the verge shaft 15,a balance wheel I 85, a balance shaft 80 and a hair spring 82.

An auxiliary seconds shaft 84 is journaled between the front" and rearplates 20, 2'2 and carries a small gear 86 which meshes with the largegear 62; As thename implies, this latter seconds shaftis adapted to berotated once everyminute.

The auxiliary seconds shaft 84 has: mounted thereon a pair of camsjointly designated at 88 and a second cam 90 the cams 88- serving-toopcrate a contact group assembly 92 andthe cam 90 serving to operate acontact group 94. The contact group assembly 92 is provided for thepurpose of controlling the sending of electrical impulses toa suitableprogram device, not shown, and the contact group 94 is provided for thepurpose of sending minute impulsesto a series of secondary clocks (notshown). The nature and the specific use of the contact group assemblies52', 92 and 9'4 form no part of the present invention, similar contactgroups being shown in the above mentioned patent to East and referencemay be had to this patent for a full disclosure of the manner in whichsuch contact groups are actuated by rotation of the minute shaft of aclock mechanism similar to that shown herein. Furthermore, for anunderstanding of the electrical circuits which operate under the controlof these contacts for the purpose of synchronizing a series of secondaryclocks, with a master clock, reference maybe had to the above mentionedpatent. to Larrabee.

The power shaft 40 is adapted to be periodically impulsed or rotatedthroughout a small increment of motion to maintain the spring 39 of thedrum assembly 4| wound and, toward this end, a synchronous electricmotor I00, which is bolted as at I04 to the casting I 0 at the rear sidethereof, is provided with a motor shaft I05, the for ward end of whichis rotatably journaled in. a bracket I08- secured as at ill) to theforward face of the casting I0. The motor shaft I06 carries thereon acam II-2, hereinafter referred to as the spring motor winding cam. Thecam H2 is designed for cooperation with a, follower roller H4 carried atthe free end of an elongated lever I'IB' which is pivoted as at I I8 tothe front faceof the casting I B. A coil spring I20'anchoredat one endto a stud I22 carried medially of the lever- II6 has its other endsecured to a bracket I24, which is adjustably secured as at I26 to thecasting I0. The spring I20 thus nor mally biases the follower roller H4into engagement with the winding cam II 2. An actuating pawl IN ispivoted on the stud I22 and is spring pressed as at I30- into engagementwith the peripheral teeth of a ratchet wheel I32 rotatably journaled ona stud I34 which projects forwardly from the casting 50. The ratchetwheel I32 has integrally formed thereon a small gear I36 which mesheswith the circumferential teeth formed on a large gear I38 mounted on andsecured to the power shaft 40. A holdingpawl I40 is pivoted on a stud I42 carried by the casting I0: and. is spring pressed as at I forcooperation with the. ratchet. wheel I32.

The shaft I06 is adapted to be continuously rotated onceeverymimiteunderthe influence of the. motor i02 and; a. consequence.v by"virtue of the follower roller: IIA whichbears against the cam I I2, thelever I; '26. is, moved in a counten clockwise direction. when thefollower roller U4 moves; outwardly on the high, region of the cam. Asthe follower moves inwardly approaching a low region. of the. cam, thepawl I28 is caused: to. rotate-the. ratchet wheel I32 in; a: clockwise;direction throughout. a. small increment. of motion to; impartmotionthrough the. trainof gears I, 38, to: the power shaft; Asexplained in the: previously mentioned patent to Rast, the. spring I20.is of such a nature that after a predetermined amount of winding of thespring 38 a con-- dition of. balance will. exist between these twosprings. so that the torque applied by the. pawl I40- to. the ratchetwheel I322 will fail to move the latter and. the follower roller I'I4will be maintained. out. of engagement with the cam Hi2 until. suchtime. as: the condition of: balance. no longerexists, thus preventingoverwinding of the spring 39.

Referring: now' ta Figs. 2 and: 3=, the shaft 60 project rearward ly ofthe rear plate 22 and. has its extreme rear end seated within asocketI50 formed. inv a shaft. I52 rotatably journaled in the rearwardlyoffset portion I 4 of the. casting: I1), the socket I150 thus: servingto lend support to. the rear end of the shaft 50. The shaft I152 extendsthrough a. boss I154: formed on the. casting I0. One input. or sunelement H56 of a diiferential assembly designated in its: entirety byI58. is mounted upon. and secured to the. shaft I52 forwardly of the.casting. IFB. This. input element IE5 is. in the form of a cup-shapedgear which is anchored to the shaft I 5.2. by: means of a set screwI601; The other input element of the diff-er ential' assembly I581 is inthe form of a planet member I62 which is secured by' means of a setscrew W to the shaft and is adapted to rotate therewith. The planetmember per se is in the form of a rectangular block- I-G'G having aplanet gear I68ljournaled atone end thereof and in. constant mesh withthe teeth formed on the cup-shaped. gear I55. The. output element of thedilrerenti'al. I-5=8: is in the. form of a gear I10. similar to the gearI 56; this'gear being mounted upon and secured to a sleeve I! Islid'ably and rotatably disposed upon a stationary bushing; I12, thelatter having one end thereof anchored in the rear plate 22'. The shaftextends completely through the stationary bushing I72 and projects into.the socket I250 of the shaft I52, as previously described. The bushingextends between the planet. member I62 and: the outside face of therearplate 22 of the: clock mechanism I8.

A regulator control arm Ill (see Figs. 3,. I and 6) ismounted on andsecured to the sleeve IN and, consequently, is. movable with the gearI10 and includes a hub portion I 1-6 and: an upwardly projecting armportion [13 having a pin I secured to its free: end and projectingforwardly of the clock mechanism IS. A regulating arm I82 is pivotallysecured to the rear plate 22 and is provided with a bifurcated end I54which straddles the regulating pin I30. The. regulating arm I82 isprovided with a. forwardly extending bifurcated. spring adjustment armI86 which straddles the hair Spring 82 near its point of support and isadapted upon angular movement tovary the effective length of the hairspring 82 and thus regulate the: speed of operationv of the escapementmechanism as: is the universal prac tice in connection with most clock;escapement mechanisms. The weight of the arm I18, pin I80 and arm I86 isoffset by means of a counterbalance IBB secured to the hub portion I16of the regulator control arm I'M.

A spring element in the form of a spider I90 surrounds the bushing I12and is provided with a plurality of spring arms I92 which bear againstthe front surface of the adjustment arm I14 with the rear portion or hubthereof bearing against the rear plate 22 of the clock mechanism, thusnormally tending to urge the arm and gear assembly I14, I'll, I'I0rearwardly to cause the teeth on the cup-shaped gear I10 to engage theplanet gear I60 associated with the planet element I62.

Referring now to Fig. 2, the front plate 20 of the clock mechanism I8has bolted or otherwise secured thereto as at I94 a magnet supportingplate I96, the outer end of this plate being maintained in fixed spacedrelationship from the rearward offset portion M of the casting I bymeans of a pillar I98. The plate I06 constitutes a support for thepreviously mentioned contact assemblies 92, 94 and it also constitutes asupport for a magnet designated in its entirety at 200.

The magnet 200 involves in its general organization an L-shaped bracket202, one arm of which is secured to the plate I86 and the other arm ofwhich pivotally carries at its free end the armature 204 of the magnet200, the pivotal connection existing by virtue of a pin and slotconnection 206. The magnet core is designated at 268. A forked member2I0 is secured in face-to-face relationship on the armature 204 and suchfaceto-face contact is maintained by means of a stud 2 I 2 and coilspring 2 I 0 which surrounds the stud and bears at one end against thehead of the stud and at the other end directly against the forked member2 I0. The free end of the forked member 2 I0 is bifurcated as at 2I6(Fig. 4) and each furcation thereof is formed with a protuberance 2IIwhich is adapted to bear against the side of the adjustment arm I'Mopposite the spring spider I92, A coil spring 2I6 is secured at one endto a medial point on the forked member 2I0 and has its other endanchored to the plate I96. The spring 2 I0 is relatively heavy and thetension thereof when in position is such as to normally overcome thetension of the spring spider I92 and thus draw the arm and gear assemblyI14, I'II, I forwardly and cause disengagement of the gear I10 from theplanet gear I68.

From the above description of parts it will be seen that uponenergization of the magnet 200, the armature 204 will be attracted sothat it will pivot in a counterclockwise direction, as viewed in Fig. 2,about its pivotal point of connection with the bracket 202 to relievethe overbalancing tension on the spring spider I92 and permit the latterto force the arm and gear assembly I", III, I10 rearwardly and thuscause engagement of the gear I'I0 with the planet gear I68.

As previously set forth, the yoke or planet member I 62 constitutes aspring driven input element for the differential assembly I58. The otherinput element for this differential assembly is in the form of thecup-shaped gear I55, while the output element of the assembly I58 is inthe form of the cup-shaped gear I'I0 whose movement controls theregulator adjustment for the escapement mechanism. The input gear I56 isadapted to be continuously driven through a train of gears that derivetheir motion from a synchronous motor 220 which is bolted as at 222 tothe casting I0. The motor 220 is provided with a drive shaft 224 (Fig.5) which projects through the casting I0 and has mounted thereon a smallgear 226 which meshes with a large gear 228 mounted on the shaft I52which is rotatably journaled in the boss I54 formed in the casting I0.On the opposite side of the casting, the shaft I52 has mounted thereonthe cup-shaped gear I56 which constitutes an input element of thedifferential assembly I58.

The synchronous electric motor 220 is adapted to be connected to thecommercial 60-cycle power line (Fig. '7) and the train of gearing 226,226, which derives its motion from this motor, is so calculatedaccording to engineering exigencies that the shaft 224 and,consequently, the output gear I10 of the differential assembly I58rotates eight times each hour or, in other words, it rotates once everyseven and one-half minutes in a clockwise direction, as viewed in Fig.6. The other input element of the differential assembly I58 is, aspreviously stated, in the form of the planet assembly I62. This latterassembly, being mounted upon and driven by the shaft 60, is

a rotated under the control of the spring wound motor escapementmechanism and the regulator arm H8 is adapted to be so positioned thatthe planet assembly makes one complete counterclockwise revolutionduring the course of each seven and one-half minutes.

It will be appreciated that, because of the fact that the planet gearI66 is in constant mesh with the teeth on the input gear I56 and becauseof the fact that the planet body I66 and gear I56 are intended to rotatein opposite directions at exactly the same rate of turning movement, theplanet gear I68 will walk, so to speak, around the circular pathprovided by the teeth on the gear I56 in such a manner that there is notendency for the teeth on the planet gear I68 to impart motion in eitherdirection to the output gear I10 when the latter is held in meshtherewith under the influence of the electromagnet 200 and its armature204. This statement holds good, of course, only when the synchronousmotor 220 is energized and in operation concurrently with the operationof the escapement mechanism to control the rotation of the shaft 60 atthe predetermined rate of speed. It may be assumed that the source ofalternating current is properly regulated at the commercial power houseto generate exactly SO-cycles per minute and in the event that theescapement mechanism is improperly adjusted, as for example, to rotatethe shaft 60 at a higher rate of speed than once every seven andone-half minutes and thus cause the master clock to run fast, the planetassembly I62 will tend to rotate in a counter-clockwise direction, asviewed in Fig. 6, at a greater rate of speed than the input gear I56which rotates in the opposite direction. As a consequence of this, theteeth on the planet gear I 62 will impart a forward thrust on the outputgear I10 tending to move the same in a counter-clockwise direction andthus, through the spring thrust element I90, impart a similar movementto the regulator arm I82. Such a movement of this latter arm willincrease the effective length of the hair spring 82 and thus slow downthe clock mechanism. It follows, conversely, that in the event theescapement mechamsm is maladjusted so as to cause the clock mechanism torun slow, the planet assembly I62 W111 rotate in a counter-clockwisedirection at a slower rate of speed than the input gear I56 will rotatein "a clockwise :direction. By virtue ;of this phenomenon, the planetgear 158 will :walk around the circumferential path provided;for it :insuch :a manner that .a back thrust will be :applied to the output gear.110 which will tend to move the regulatorarm 1 18 ina clockwisedirection and thus gradually shorten the effective .length of thehairspring to thereby quicken the oscillatory movement .of theescapement wheel 18 and speed up the clock mechanism. Such movement ofthe regulating arm I18 continues until a degree .of balance existsbetween :the speed-of the GO-cycle synchronouselectric drive mechanismand the speed of the spring wound .motor drive mechanism, at which timethe master clock may be assumed to be operating at the proper rate ofspeed.

Referring now to Fig. -6, wherein asimple electrical circuit for theoperation of the master clock is shown, it will be seen that the twosynchronous motors l flfland 220, as well as the magnet 200, are allarranged in parallel with the source of 60-cycle alternating current sothat in the event there is a power failure and current is interruptedall three of these elements become simultaneously deenergized, thuscausing the motor 220 to .stop .and as a consequence, the input gear['56 to cease .its rotation. At the same time, the magnet 200 becomesdeenergized and the armature 204 is released under the influence of thespring 2l8 so that the bifurcated arm 2!!! will draw the output gear 110out of mesh with the planet gear I68 and prevent movement of theregulating arm L78 which would ordinarily occur in the .event that thesegears were allowed to remain in mesh after power failure. 'Uponsubsequent restoration of the power supply, the magnet r200 againbecomes energized and the output gear 118 and planet gear 168 are againthrown into mesh under the influence of the armature 204 .and forked arm2 ID. Any discrepancy that may have arisen during the interim of powerfailure will then be automati-,- cally corrected by the differentialassembly 158 in the manner previously described.

It should be noted that in the event of failure of the escapementmechanism of the .master clock, as for example, due to theilodgement oflint or other foreign surfaces in the hearings or other parts of theclock .mechanism, the :synchronous motor will continue to rotate whilethe planet assembly 162 will remain stationary as far as its revolutionabout the axis of the shaft 60 is concerned. In such an event, the inputgear I56 will rotate the planet gear in such a manner as to cause theoutput gear I'm to rotate in a clockwise direction, as viewed in Fig. 6,to bring theregulator arm I18 to the limit of :its fast adjustment. Themaster clock will then be set for-a fast adjustment and when the same isagain started and the condition which caused its failure remedied by theoperator, automatic readjustment "of the regulator arm I78 will takeplace and there will be no need for the operator to 'effectmanualadjustment of the regulator arm. It should'be observed that during theperiod of idleness of the master clock after the regulator arm hasreached the limit of its fast adjustmentslippage will occur between thethree-armed friction spring I90 and the forward surface of the regulator.arm I18. At no time will the driving connection between theclock'mechanism and the regulator arm [14 become disengaged and theoperator will at .all

times be freed pf any responsibility associated 226 and the teeth .252on this disc are designed for cooperation with an operating finger 254.formingpartof a contact group assembly designated .in its entirety at2.56, thislatter assembly being secured by means of a bracket 253 to therear :face of :the casting M. A pair of contacts are associated with theassembly 256 and are adapted upon synchronous rotation of the disc 2.50to become closed momentarily once every :two seconds for the purpose ofsending rapid impulses :to a series of secondary clocks=(not shown)associated with the master clock comprising the present invention duringthe synjchronizing period in accordance 'with the principles setforth inthe above mentioned patent to Bryce.

While there havebeen shown and described and pointed .out thefundamental novel features of the invention as applied to a preferredembodiment, it will :be understood that various omissions andsubstitutions and changes in the form and details of the apparatusillustrated and in its operation may be made by those skilled in theart, Without :departing from the spirit of the invention. It is theintention, therefore, to be limited only as indicated by the scope ofthe following claims.

What is claimed is:

1. In aclock system,a.source-ofcurrentsupply, asynchronous motorrotating in timed relationship with said source,a difierential assemblyincluding a sun gear comprising one input element of the assembly, aplanet gear in constant mesh with said sun gear and constituting anotherinput element of the diiferential assembly and a second sun :gearnormally out of mesh with said planet gear: and capable .of being movedto a position wherein it is in engagement with said planehgear,saidzlatter sun gear-constituting the output element of :saiddifferential, means operatively connecting .said synchronous motor tosaid first sun gear in driving relationship, a spring driven clockescapement mechanism including a drivenshaft operatively connected tothe planet gear for revolving the latter about the axis of said firstsun gear in a direction whose effect on the .second sun gear is opposedto the effect of .said first sun gear, a regulating member for said.clock escapement mechanism operatively connected thereto and movable inone direction .to progressively lengthen the natural period of saidescapement mechanism and movable in the other direction to shorten saidperiod, the natural period or" said escape ment mechanism within itslimits of adjustment being such as to cause said *input elements to bedriven at rates "of speed wherein little or no motion is applied to saidsecond sun gear, and means connecting said second sun gear andregulatingmember for imparting the movements of the former to the latterto thereby regulate the natural period of .said escapement mechanism inaccordance with the movement of said synchronous motor, .anelectromagnet operatively connected to.said sour.ce of power andnormally energized thereby, an armature for saidelectromagnet,meansoperati-vely connecting. said .armae ture .and second .sun gearand-serving to .main-v tain the latter in mesh with said planet gearwhen the electromagnet is energized.

2. In a clock system, a source of current supply, a synchronous motorrotating in timed relationship with said source, a differential assemblyincluding a sun gear comprising one input element of the assembly, aplanet gear in constant mesh with said sun gear and constituting anotherinput element of the differential assembly and a second sun gearnormally out of mesh with said planet gear and capable of being moved toa position wherein it is in engagement with said planet gear, saidlatter sun gear constituting the output element of said differential,means operatively connecting said synchronous motor to said first sungear in driving relationship, a spring driven clock escapement mechanismincluding a driven shaft operatively connected to the planet gear forrevolving the latter about the axis of said first sun gear in adirection whose effect on the second sun gear is opposed to the effectof said first sun gear, a regulating member for said clock escapementmechanism operatively connected thereto and movable in one direction toprogressively lengthen the natural period of said escapement mechanismand movable in the other direction to shorten said period, the naturalperiod of said escapement mechanism within its limits of adjustmentbeing such as to cause said input elements to be driven at rates ofspeed wherein little or no motion is applied to said second sun gear,and means operatively connecting said second sun gear and regulating"arm for imparting the movement of the former to the latter to therebybring the natural period of said escapement mechanism into conformitywith the rate of rotation of said synchronous motor, the said connectingmeans normally being yieldable with respect to the said gear and arm topermit reverse rotation therebetween, said connecting means yieldingindependently of the said gear and arm, an electromagnet operativelyconnected to said source of power and normally energized thereby, anarmature for said electromagnet, means peratively connecting saidarmature and second sun gear and serving to maintain the latter in meshwith said planet gear when the electromagnet is energized. 3. In a clocksystem, a source of alternating current supply, a synchronous motorrotating in timed relationship with said source, a difierential assemblyincluding a pair of input elements and an output element whose movementsare a differential function of said input elements, means operativelyconnecting said synchronous motor to one of said input elements indriving relationship, a spring driven clock escapement mechanismincluding a driven shaft operatively connected to the other inputelement of the differential assembly in driving relationship for drivingthe latter in a direction Whose effect on the output element is opposedto the effect of said first input element, a regulating member for saidclock escapement mechanism operatively connected thereto and movablefrom an advanced position to a retracted position for progressivelylengthening the natural period of said escapement mechanism and movablein the other direction to shorten said period, the natural period ofsaid escapement mechanism within its limits of adjustment by theregulating member being such as to cause said input elements to bedriven at respective rates of speed closely approaching or equaling eachother, regulating member driving means for adjusting said regulatingmember in accordance with the movements of the output element of saiddiflereiitial assembly, a slip clutch comprising a friction springinterposed between a stationary frame plate and said regulating memberdriving means adapted to provide both a yielding connection between saidclock escapement mechanism and said synchronous motor at any time theclock escapement mechanism should become inoperative and also a drivingconnection between said output element of the differential assembly andsaid driving means for the regulating member at all times duringsimultaneous operation of both said clock escapement mechanism and saidsynchronous motor whereby the natural period of said escapementmechanism is regulated by the rate of speed of said synchronous motorunder the control of said source of current supply, during simultaneousoperation or the escapement mechanism and the motor.

4. In a clock system, a source of alternating current supply, asynchronous motor rotating in timed relationship with said source, adiiierential assembly including a pair of input elements and an outputelement Whose movements are a differential function of said inputelements, means operatively connecting said synchronous motor to one ofsaid input elements in driving relationship, a spring driven clockescapement mechanism including a driven shaft operatively connected tothe other input element of the diiferential assembly in drivingrelationship for driving the latter in a direction whose effect on theoutput element is opposed to the effect of said first input element, aregulating member for said clock escapement mechanism operativelyconnected thereto and movable from an advanced position to a retractedposition for progressively lengthening the natural period of saidescapement mechanism and movable in the other direction to shorten saidperiod, the natural period of said escapement mechanism within itslimits of adjustment by the regulating member being such as to causesaid input elements to be driven at respective rates of speed closelyapproaching or equaling each other, and a safety mechanism forpreventing damage to said clock escapement mechanism by said synchronousmotor comprising means for driving said regulating member between fixedlimits, a friction spring slip clutch member interposed between astationary frame member and the driving means for said regulating memberadapted to provide a driving connection for said regulating memberwithin the limits of its adjustment and a yielding connection wheneverthe rate ratio between the clock escapement and the synchronous motor issuch that the synchronous motor acts to drive the regulating memberbeyond either of its two extreme limits of adjustment, said safetymechanism normally permitting the dilferential assembly to impart to theregulating member rotational movements in either direction to advance orretard the same and to thereby regulate the natural period of saidescapement mechanism in accordance with the frequency of the said sourceof current supply.

' REYNOLD BL JOHNSON.

EDWARD F. GEIGE'R.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 1,328,247 Poole Jan. 13, 1920 1,687,491 Bryce Oct. 16, 19281,878,931 Larrabee Sept. 20, 1932 2,424,119 Rast July 15, 1947

